Finding area bounded Supposedly easy yet I have no clue

In summary, a problem of this type can be solved by multiplying the left endpoint height by the right endpoint height and summing them up.
  • #1
tjohn101
93
0

Homework Statement


Use the left endpoint graph with the given number of
rectangles to approximate the area bounded by the
curve f (x), the x-axis, and the line x = 4.
f(x)=x2+x

Homework Equations


No idea.


The Attempt at a Solution


Once again, not a clue how to start this.
 

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  • #2
tjohn101 said:

Homework Statement


Use the left endpoint graph with the given number of
rectangles to approximate the area bounded by the
curve f (x), the x-axis, and the line x = 4.
f(x)=x2+x

Homework Equations


No idea.

The Attempt at a Solution


Once again, not a clue how to start this.

Well, you are calculating the area of each rectangle, and then adding the areas up. You are using 4 rectangles from (0,4). So, you know the length of each rectangle. How do you find the height? Look at where the rectangles touch the graph (i.e., the left endpoint of the rectangle).
 
  • #3
Okay, I kind of guessed my way through it based on my notes and came up with 88/3 or 29.3333_ . Now, the next question asks me to do the same thing, but use the right endpoint graph. Wouldn't the answers be the same?
 
  • #4
tjohn101 said:
Okay, I kind of guessed my way through it based on my notes and came up with 88/3 or 29.3333_ . Now, the next question asks me to do the same thing, but use the right endpoint graph. Wouldn't the answers be the same?

You are splitting up the interval (0,4) like this:

(0, 1) (1, 2) (2, 3) (3, 4).

Do you see which are the left and right endpoints?
 
  • #5
tjohn101 said:
Okay, I kind of guessed my way through it based on my notes and came up with 88/3 or 29.3333_ . Now, the next question asks me to do the same thing, but use the right endpoint graph. Wouldn't the answers be the same?
What did you do to calculate this? I came up with a different answer.
 
  • #6
So for the left endpoints I just do A=b*h and then add them all up?

Same for the right?
 
  • #7
tjohn101 said:
So for the left endpoints I just do A=b*h and then add them all up?

Same for the right?
Yep, that's really all there is to a problem of this type. You want to split up the interval, calculate the height at whichever point you're using (left, right, mid), calculate the area of each rectangle, and sum them up.

This all leads into how to calculate the REAL area under the curve, which basically has to do with splitting the interval into infinitely many rectangles!
 
  • #8
Yeah that's what I'm doing now. That part's okay. Just a little long.
 

FAQ: Finding area bounded Supposedly easy yet I have no clue

What is the formula for finding the area of a bounded shape?

The formula for finding the area of a bounded shape is different for each shape. For example, the formula for finding the area of a rectangle is length x width, while the formula for finding the area of a circle is pi x radius squared.

What is the difference between area and perimeter?

Area is the measurement of the surface inside a shape, while perimeter is the measurement of the distance around the outside of a shape. In other words, area is the amount of space inside a shape, and perimeter is the length of the boundary of a shape.

How do I find the area of a shape with irregular boundaries?

To find the area of a shape with irregular boundaries, you can break it up into smaller, simpler shapes and find the area of each individual shape. Then, you can add the areas of all the smaller shapes together to find the total area of the irregular shape.

What is the easiest way to find the area of a triangle?

The easiest way to find the area of a triangle is to use the formula: 1/2 x base x height. The base and height of a triangle can be easily measured or calculated, making this formula relatively simple to use.

How can I check my answer when finding the area of a bounded shape?

You can check your answer by using another method to find the area. For example, if you used the formula for finding the area of a rectangle, you can also divide the rectangle into smaller squares and add up their areas to check your answer. Additionally, you can use an online calculator or ask a friend or teacher to verify your answer.

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